47 C.F.R. § 1.294
Oppositions and replies
(a) Any party to a hearing proceeding may file an opposition to an interlocutory request filed in that proceeding.
(b) Except as provided in paragraph (c) of this section or as otherwise ordered by the presiding officer, oppositions to interlocutory requests shall be filed within 4 days after the original pleading is filed, and replies to oppositions will not be entertained.
(c) Additional pleadings may be filed only if specifically requested or authorized by the person(s) who is to make the ruling.